In the WA and Scottish Highway regulations manual it says this:
"2.1 There are many definitions of hazard and risk; for the purpose of this Standard, the following definitions shall be used.
HAZARD: A hazard is a feature (e.g. embankment) or object (e.g. lighting column) that can cause harm or loss. Harm or loss can be physical, financial or economic, strategic, or be time-based, or any combination of these.
RISK: A risk is the chance, high or low, that somebody or something will be harmed by the hazard.
2.2 In general terms, in this Road Restraint Systems (RRS) Standard, risk can further be described as the likelihood of the hazard being reached or hit by an errant vehicle (chance) multiplied by the resulting consequence if the hazard is reached or hit (harm). The hazard may be within or beyond the highway boundary. A risk may also occur if a hazard that is hit by an errant vehicle falls, or becomes detached and forms a projectile, and causes an injury to Others or causes further damage. The consequence may, for example, be: injury to an occupant of the errant vehicle; temporary loss of a strategic installation; adverse affect on Others; etc."
Clear as mud, as you'd imagine.